Note: There is enough filling to make 4 dozen gyozas. The amount of sauce
indicated above is enough for 12 gyozas. If you want to make more, multiple
the sauce ingredients, but bear in mind that you will have to make the
sauce separately as part of each batch. Freeze extra uncooked gyozas on a
baking sheet; when frozen, transfer them to a freezer bag. Do not defrost
before browning.